If you want to see a roomful of people roll their eyes, just walk into a gathering of astronomers — or experts on ancient Mesoamerican civilizations, for that matter — and shout, “Mayan apocalypse!” For years now, the idea that the earth will be destroyed in a terrible cataclysm on Dec. 21, 2012, has been bouncing around the Internet and showing up in articles, books and even movies. It’s been the inspiration for get-rich-quick schemes. It’s like Y2K all over again, but at least that episode of end-of-world hysteria was reality-based.

The 2012 apocalypse, by contrast, is just plain nutty. An asteroid is not about to hit the earth. Neither is an imaginary planet called Nibiru. Our world isn’t going to be abruptly flipped upside down like a burger on a griddle. The earth won’t be plunged into a three-day blackout. And contrary to what you’ve been hearing, Maya astrologers never said any of that stuff would actually happen. The idea is so preposterous that a Web search for “Mayan apocalypse” turns up as many spoofs as it does serious discussions.

The truth is a lot more prosaic than what the tinfoil-hat crowd would have you believe. Yes, the Maya had what’s known as a Long Count calendar, and yes, that calendar ends on Dec. 21, 2012. But the delightful thing about calendars — including the one the Maya used — is that they always start over again from zero. Just because we have a record of the Long Count equivalent of last year doesn’t mean the Maya weren’t busy working on next year’s. As for Nibiru, well, never mind. That one was borrowed from the ancient Sumerians, and the original prediction was that we’d get clobbered by the free-range planet in 2003. You might have noticed that that didn’t happen, so the date of arrival was moved up to 2012 to coincide with the Maya silliness. An apocalyptic twofer!

All the same, some folks at NASA are seriously worried — not about the end of the world but about the real harm the loose talk may be doing to some people’s mental health. “I get a tremendous number of e-mails about it,” says David Morrison, a space scientist at the NASA Ames Research Center at Moffett Field in California, who hosts the agency’s Ask an Astrobiologist website. “A large fraction are from people asking if the world will end, saying they’re scared and don’t know what to do. A few even talk about suicide.”

It might seem implausible that people would kill themselves over an imaginary cosmic event, but it happened back in 1997, when 39 members of the Heaven’s Gate cult in Southern California committed mass suicide under the delusion that the approach of Comet Hale-Bopp meant it was time to leave their physical bodies. Fearing that people were taking the 2012 scaremongering too seriously, NASA convened a Google+ hangout on Nov. 28 during which people could interact with six astronomers who were prepared to debunk any myth the public could throw at them. For nearly an hour, they did just that, patiently explaining, for example, that any asteroid en route to obliterating earth in just a few short weeks would have been spotted by telescopes long ago and that Nibiru, one of whose leading proponents is a woman who insists she’s in touch with aliens from the Zeta Reticuli star system, would be the brightest object in the sky after the sun and moon.

But NASA has been debunking the apocalypse for years now, in the same patient and rational manner, and it hasn’t helped a whole lot. “I’m told that about 10% of the public believes this stuff,” says Seth Shostak, a scientist with the SETI Institute in Mountain View, Calif., who wasn’t part of the online hangout. “That’s about the same percentage that believes in Santa Claus and thinks we never went to the moon.”

Trying to reduce that percentage by providing facts isn’t necessarily going to work, since proponents of the nonsense provide plenty of their own “facts.” “I have to admit,” says Morrison, “that there’s something of an inherent contradiction when we scientists tell people not to trust things they read on the Internet, and then put information on the Internet.”

The real problem, said Andrew Fraknoi, an astronomer at Foothill College in Los Altos, Calif., during the NASA webcast, “is that our schools have not taught skeptical thinking, have not taught children to distinguish between fantasy and reality. The real threat in 2012 is the public’s low level of science understanding.”

Whether that could lead to panic or suicides this time around is unclear. Only a tiny handful of the thousands of worried e-mails Morrison has gotten raise the disturbing possibility of people taking their own lives, and those have all been from adults.

But even if kids are not suicidal, plenty of them are frightened, and have been for a long time. “Two years ago, I met with a group of middle-school science teachers,” Morrison says, “and I asked them how many of them were seeing kids who were worried about 2012. Nearly every hand shot up.” When Dec. 21 comes and goes without incident, those fears should finally evaporate — that is, until the next doomsday pronouncement comes along.